.container{
    width: 800px;
    margin: 0 auto;
}
.left{
    float: left;
    width: 300px;
    height: 400px;
    background: lightblue;
}
.right{
    margin-left: 300px;
    width: 500px;
    height: 400px;
    background: lightcoral;
}
.header,.footer{
    background: #CCCCCC;
    height: 100px;
}
